Which of these numbers is prime? ${8,\ 27,\ 51,\ 53,\ 95}$
Explanation: A prime number has exactly two factors: 1 and itself. The factors of 8 are 1, 2, 4, and 8. The factors of 27 are 1, 3, 9, and 27. The factors of 51 are 1, 3, 17, and 51. The factors of 53 are 1 and 53. The factors of 95 are 1, 5, 19, and 95. Thus, 53 is a prime number.